Electron discharge device



June 8, 1937. N R, 5 |TH 2,082,851

' ELECTRON DISCHARGE DEVICE Filed April 2'7, 1955 INVENTOR NEWELL R. SMITH ATTORNEY ie discs.

Patented June 8, 1937 PATENT OFFICE v 2.082.851 ELECTRON mscnaaon DEVICE Newell a. Smith, Bloomfield, N. 1., mam, by mesne assignments, to Radio Corporation of America, New York,-N. Y., a corporation of Delaware Application April 27, 1935, Serial No. 18,554

This invention relates to electron discharge devices of the type employing metal envelopes and more particularly to the arrangement of electrodes and getter shields in said envelopes.

In the manufacture of the modern receiver type electron tubes it is customary to assemble the electrodes as a unitary structure with the cathode and side rods of the grids and anode held in fixed spaced relation by spacers such as mica or ceram- This unitary assembly-of electrodes is mounted within the envelope with the edges of at least one of the mica discs bearing against the inner wall of the envelope to centrally position the electrode assembly within the envelope. In an electron tube with a metal envelope. where the envelope is operated at a potential diiferent from that of the electrodes. troublesome leakage paths are apt to be established over the surfaces of the mica spacers between the envelope and electrodes. These leakage paths become particularly objectionable if getter material is deposited on the mica spacers.

The principal object of my invention is to provide an improved arrangement of parts in an electron discharge device whereby leakage over insulating members of the device is minimized.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, will be best understood by reference to the following description taken in connection with the accompanying drawing in which Figure l is a perspective view with parts broken away of one type of tube made in accordance with my invention; Figure 2 shows a modification of a combined getter shield and spacer; and Figure 3 shows a modification of a gettercup support.

The tube shown in Figure 1, as representative of the types of tubes in which my invention may be employed, comprises a sealed metallic envelope made up of a sleeve-shaped shell l0 closed. at its lower end by a header l i, which in the embodiment shown carries the electrode assembly. The electrodes by way of example have been shown as a cathode l2, grid l3 and anode l4 concentrically arranged and secured in' fixed spaced relation by insulating spacers l5. Ap-

propriate lead-in wires to the several electrodes are insulatingly sealed in eyelets in the header as shown. The electrode assembly is supported upon the header by a U-shaped bracket with upstanding legs l6 and a horizontal tying portion I! which is welded or otherwise suitably secured to the upper face of the header. The subject matter of the supporting bracket 16, I1 is more assignee as this application.

So the maximum length of leakage paths may be provided between the high potential anode and grids and the metal envelope over the surfaces of the spacers IS, the insulating spacers are smaller than the envelope shell so that their edges are spaced from the walls of the metal envelope. The electrode assembly is centered and braced in the envelope by a metal disc l8. As will hereinafter more fully appear, disc 18 not only functions as a centering and steadying means but serves as a shield to prevent the deposition of getter material on the insulating spacer I 5. Disc I8 is secured to'the upper end of the electrode assembly, preferably by up-turned tabs i9 welded to extensions 20 of the supporting side rods 16, and its diameter is slightly less than the internal diameter of the shell of the envelope. Depending tabs or spring fingers 2!, on oposite sides of the disc l8, may conveniently be stamped from a sheet of metal with the disc, and bent or tapered outwardly so that the diametrical distance between the lower edges of the tabs is slightly greater than the internal diameter of the envelope shell. This construction affords convenient yieldable spacing or centering means between the envelope shell and the disc IS with its attached electrode mount. A getter pellet 22 of the usual gettering material may be suitably secured in the dome of the envelope above the level of disc l8 by a mesh basket as shown.

In manufacture it has been found convenient to assemble the electrodes as a unitary structure between the spacers l5 and then mount the assembly upon the legs [6 of the bracket, which in turn is welded or brazed to header ll. Disc [8 may then be secured to the upper ends of extensions 20 of the legs or side rods I 6 as above described. In a separate operation the getter may be secured in the dome of the envelope shell l0 after which the shell may be lowered over the electrode assembly and its lower rim sealed gastight to the header as shown. An .electron discharge device constructed in accordance with myv invention is characterized by the firmness and accuracy with which the electrodes are centered within the envelope as well as by the eflicient manner in which the electrodes and spacers are shielded from getter material.

In the modification shown in Figure 2 the centering disc I 8 is split inwardly from the edges of the depending spring fingers 2| to form tabs 28 which are folded over and welded or brazed to the upper ends of the supporting rods 20.

In Figure 3 a getter support cup 3| is shown as resiliently supported from the centering disc l8 by spring finger 32. This construction serves to eliminate the necessity of securing the getter pellet in the dome of the shell of the envelope.

The embodiment of the invention illustrated and described herein has been selected for the purpose of clearly setting forth the principles involved. It will be apparent however, that the invention is susceptible of being modified without departing from the spirit and scope of the invention and I, therefore, aim to cover by the appended claims all modifications within the scope of my invention.

I claim:

1. An electron discharge device comprising a metal envelope, a getter holder secured to the inner wall of said envelope, two parallel support rods secured internally of said envelope, two insulating spacing members secured between said support rods, a cathode with cooperating grid and anode electrodes mounted on and between said spacing members, a centering member secured between said support rods outwardly from said spacing members and yieldingly abutting the inner wall of said' envelope, said centering memher having a central imperforate portion to shield said insulating members from said getter holder.

2. An electron discharge device comprising a cylindrical metal envelope closed at its upper end with an integral dome-shaped section and closed at the lower end with a metal header, spaced parallel supporting rods extending longitudinally of said envelope and secured at one end to said header, an electrode assembly secured between said rods intermediate their ends, a transverse metal disc of slightly less diameter than the diameter of said envelope welded to the upper end 01 said rods above said electrode assembly, and a getter attached centrally to said 20 dome-shaped section over the center of said disc.

NEWELL R. SMITH. 

